Process for plant defoliation



United States Patent 3,359,092 PROCESS FOR PLANT DEFOLIATION Milton L.Dunham, Jr., Tonawanda, and Francis M. OConnor, Kenmore, N .Y.,assignors to Union Carbide Corporation, a corporation of New York NoDrawing. Original application Sept. 20, 1961, Ser. No. 139,370, nowPatent No. 3,234,028, dated Feb. 8, 1966. Divided and this applicationFeb. 2, 1966, Ser. No. 538,879

2 Claims. (Cl. 7170) This application is a division of application S.N.139,- 370, filed Sept. 20, 1961, now US. Patent No. 3,234,028.

This invention relates to agents for use in chemical reactions andprocesses for their use. More particularly the invention relates toagents from which materials can be released at an appropriate time toact as reactants or catalysts in chemical reactions. The agents of theinvention may be used as carriers of aromas, defoliants, phamaceuticals,and bleaching agents for example.

It is an object of the present invention to provide an agent whichcontains materials that are to participate in or promote a chemicalreaction and which retains these materials until their release isdesired.

The objects of the invention are accomplished by adsorbing theappropriate material with a Zeolitic molecular sieve. The resultingagent may be blended with other materials and their release controlledwith the beneficial results which will appear from the examples andtests described below.

Zeolitic molecular sieves, both natural and synthetic, aremetal-aluminum-silicates. The crystalline structure of these materialsis such that a relatively large sorption area is present inside eachcrystal. Access to this area is by way of openings or pores in thecrystal. Molecules are selectively adsorbed by molecular sieves on thebasis of size and polarity among other things.

To facilitate an understanding of the terms used in the examples andclaims appearing below, some of the synthetic Zeolitic molecular sievesused in making the curing agent of the invention will be described. Forconvenience one of the synthetic molecular sieves used has beendesignated zeolite X and is described, together with a process formaking it, in detail in United States patent application Ser. No.400,389 filed Dec. 24, 1953, now US. Patent No. 2,882,244.

The general formula for zeolite X, expressed in terms of mol fractionsof oxides is as follows:

In the formula M represents a metal and n its valence. The zeolite isactivated or made capable of adsorbing certain molecules by the removalof water from the crystal as by heating. Thus the actual number of molsof water present in the crystal will depend upon the degree ofdehydration or activation of the crystal.

The metal represented in the formula above by the letter M can bechanged by conventional ion exchange techniques. The sodium form of thezeolite, designated sodium zeolite X, is the most convenient tomanufacture. For this reason the other forms of zeolite X are usuallyobtained by the modification of sodium zeolite X.

A typical formula for sodium zeolite X is 1 in preparing the agents ofthe invention.

The major lines in the X-ray diffraction pattern of sodium zeolite X areset forth in Table A below:

TABLE A d value of reflection in A.: I I/I l4.42:0.2 100 8.82:0.1 18 441:0.05 9 3 8010.05 21 3 33:0.05 18 2 88:0.05 19 2 79:0.05 8 2.66i0.05 8

In Obtaining the X-ray diffraction powder patterns, standard techniqueswere employed. The radiation was the K doublet of copper, and a Geigercounter spectrometer with a strip chart pen recorder was used. The peakheights, I, and the positions as a function of 20, Where 0 is the Braggangle, were read from the spectrometer chart. From these, d(obs.), theinterplanar spacing in A., corresponding to the recorded lines wascalculated. The X-ray patterns indicate a cubic unit cell of dimensionsbetween 24.5 A. and 25.5 A.

To make sodium zeolite X reactants are mixed in aqueous solution andheld at about 100 C. until the crystals of zeolite X are formed.Preferably the reactants should be such that in the solution thefollowing ratios prevail:

'SiO /Al O s-s Na O/SiO 1.2-1.5 H O/Na O 3540 The manner in whichzeolite X might be obtained is illustrated by the following: 10 grams ofNaAlO 32 grams of an aqueous solution containing by weight about 20% NaO and 32% SiO 5.5 grams NaOH and cc. H O were mixed and held in anautoclave for 47 hours at about 100 C. Crystalline zeolite X wasrecovered by filtering the reacted materials and washed with water untilthe pH of the effiuent wash water is between 9 and 12. The crystals aredried after which they are ready for use in making the agent of theinvention.

Another synthetic Zeolitic molecular sieve which has been successfullyused in preparing a curing agent according to the invention has beendesignated zeolite A and is described in detail together with processesfor its preparation in United States patent application Ser. No.400,388, filed Dec. 24, 1953, now US. Patent No. 2,882,243.

The general formula for zeolite A, expressed in terms of mol fractionsof oxides is as follows:

In the formula M represents a metal, hydrogen, or ammonium, n thevalence of M. The amount of H 0 present in zeolite A will of coursedepend on the degree of dehydration of the crystals.

As in the case of zeolite X and other zeolites, the element or groupdesignated by M in the formula can be changed by conventional ionexchange techniques. Sodium zeolite A is the most convenient form toprepare and other forms are usually obtained from it by an ex change ofions in aqueous solutions. A typical formula for sodium zeolite A is0.99

The removal of at least part of the water, as by heating, would besuflicien-t to prepare the sodium zeolite A for use in making the agentof the invention.

Using the techniques by which the X-ray diffraction data for sodiumzeolite X was obtained, similar data for sodium zeolite A was obtainedand is recorded in Table B.

3 TABLE B a' value of reflection in A.: 100l/I 12.2:02 100 8.6102 697.05:0.15 35 4.071008 36 3.68:0.07 53 3.381006 16 3.26:0.05 47 3.96:0.0555 2.73:0.05 12 2.601005 22 To make sodium zeolite A reactants are mixedin aqueous solution and held at about 100 C. until crystals of sodiumzeolite A are formed. The reactants should be such that in the solutionthe following ratios prevail:

SiO /Al O 1.3-2.5 Na O/SiO 0.8-3.0 Hgo/Nazo An example of the manner inwhich Zeolite A may be prepared is as follows: 80 grams of NaAlO 126grams of an aqueous solution of sodium silicate containing about 7.5% byweight Na O and 25.8% by Weight SiO and 320 cubic centimeters of H wereplaced in an autoclave. In the autoclave the following ratios prevailed:SiO /Al O l.2-, Na O/SiO 1.2, and H O/Na O36. The contents of theautoclave were held at about 100 C. for about 12 hours. Crystallinezeolite A was recovered by filtration and washed with distilled wateruntil the effluent wash Water had a pH of between 9 and 12. After dryingand dehydration the crystals are ready for use in making the agents ofthe invention.

The manner in which the agents of the invention may be made and used canbe seen from the following examples.

Example I Ethylene is known to effect the defoliation of cot-ton plants.Difficulties are experienced in applying ethylene to the plants. Theproblem can be solved with the agents of the invention.

A sample of sodium zeolite A was dehydrated and ethylene was introducedinto a chamber containing the dehydrated zeolite. Ethylene was adsorbedby the zeolite. Cotton plants were placed under a jar with one gram ofthe sample which contained 5.8 weight-percent adsorbed ethylene. Theplant was completely defoliated in four days indicating gradual andeffective release of the ethylene.

Ethylene is known to be effective as a ripening agent for bananas. Thecontrol of this ripening process can be improved by using the agents ofthe invention as Will be seen in Example 11.

Example II Green bananas were placed in polyethylene bags, whichincluded a small quantity of zeolite A containing ethylene. The bagswere stored in the dark for two weeks at 10 C. The bananas showedevidence of ripening greater than did bananas stored under the sameconditions out of the presence of ethylene. The controlled release ofthe ripening agent, ethylene, was demonstrated by this test.

Because molecular sieves will adsorb vapors and retain them for longperiods of time or until released by heating or otherwise, the molecularsieves are useful in retain'mg aromas until their release is desired. InExample III the adsorption and release of an aroma with a number ofmolecular sieves and the release of the aroma by a number of means aredescribed.

Example 111 Pellets of sodium zeolite A, pellets of calcium zeolite Aand pellets of sodium zeolite X were each activated and subjected to astream of gases carrying the aroma emitted from roasted coffee grounds.Samples of each type of pellet were then held in a stream of carbondioxide. The carbon dioxide was adsorbed by the molecular sievesreleasing the coffee aroma in each instance. Similar results wereobtained when moist air was passed over the aroma laden crystals.

The use of molecular sieves to hold aromas until their release isdesired can of course be employed in products other than coffee. Forexample, the presence of molecular sieves, laden with the aroma ofcooked food, can be advantageously added to dehydrated food products.Perfume or the like adsorbed by the molecular sieves can be placed insoap where it will be released when the soap and the molecular sieve arewetted. Similarly, a perfume or aroma in a molecular sieve can bereleased by the burning of a wax candle which contains the treatedmolecular sieve.

Pharmaceutical agents can be adsorbed on molecular sieves and theirapplication and effectiveness improved. Agents which have a germicidaleffect on bacteria causing athletes foot can be adsorbed by themolecular sieve and dusted over the infected skin area. As the sieveadsorbs moisture from the body, the germicidal agent is released. Inaddition to supplying a germicide the preparation tends to effect thedrying of the skin. This drying action might also be used in thetreatment of burns. Pumigants such as hydrogen sulfide can be adsorbedand released slowly where and when needed by the application of moistureto the molecular sieve.

The adsorptive capacity of the molecular sieves for bleaching agents,such as chlorine and hydrogen peroxide, make them useful in thebleaching of many materials, for example paper, where moisture ispresent to desorb the bleaching agent.

The agents of the invention may also be employed to introduce normallygaseous materials into liquid fuels. Butane, for example, may beadsorbed and entrained in gasoline or kerosene. The butane will bereleased by the heat of the combustion of the fuel.

These examples of the use of the agents of the invention serve toillustrate the manner in which they might be used. Molecular sievesother than those mentioned in the specification may be satisfactorilyemployed within the scope of the invention. Chabazite, mordenite andfaujasite are examples of naturally occurring molecular sieves thatperform satisfactorily in the practice of the invention.

What is claimed is:

1. A process for plant defoliation of a plant susceptible to defoliationby contact with ethylene comprising the steps of adsorbing ethylene ondehydrated crystalline zeolitic molecular sieve, contacting adefoliating amount of the ethylene-containing molecular sieve withmoisturecontaining air in the immediate proximity of said plant therebycontrollably releasing substantially all of said ethylene from saidmolecular sieve for contact with and defoliation of said plant.

2. A process according to claim 1 in which zeolite A is said crystallitezeolitic molecular sieve and cotton is said plant.

References Cited UNITED STATES PATENTS 2,245,867 6/1941 Mehrlich 7l-2.42,358,882 9/1944 Rohrbavgh 71-2.4 X 2,882,243 4/ 1959 Milton. 3,036,9805/1962 Dunham et al 2603l.4

OTHER REFERENCES Ahlgren et al.: Principles of Weed Control, I. Wiley &Sons, New York, 1951, p. 272.

Seeliger, Chemical Abstracts, vol. 16, pp. 1170 and 1 171.

JAMES O. THOMAS, J 11., Primary Examiner.

1. A PROCESS FOR PLANT DEFOLIATION OF A PLANT SUSCEPTIBLE TO DEFOLIATIONBY CONTACT WITH ETHYLENE COMPRISING THE STEPS OF ABSORING ETHYLENE ONDEHYDRATED CRYSTALLINE ZEOLITIC MOLECULAR SIEVE, CONTACTING ADEFOLIATING AMOUNT OF THE ETHYLENE-CONTAINING MOLECULAR SIEVE WITHMOISTURECONTAINING AIR IN THE IMMEDIATE PROXIMITY OF SAID PLANT THEREBYCONTROLLABLY RELEASING SUBSTANTIALLY ALL OF SAID ETHYLENE FROM SAIDMOLECULAR SIEVE FOR CONTACT WITH AND DEFOLIATION OF SAID PLANT.